By ERIC WEINER

Published: June 11, 1989

When Thomas G. Plaskett became chairman of the Pan Am Corporation last year, a large map depicting what remained of the airline's once vast worldwide route system adorned the hall outside his office. But Mr. Plaskett soon had the map removed. ''I couldn't bear to look at it every day,'' he said.

All that could change if the financially fragile carrier succeeds in its bold bid for NWA Inc., the parent of Northwest Airlines, a profitable carrier half again its size. The product of such a merger would be the largest international airline in the Western world, with a route system spanning five continents, and would be surpassed only by Aeroflot, the Soviet airline.

Some industry analysts agree that Northwest and Pan Am are a good match. For Pan Am, which has lost nearly $800 million since 1986 and sold a number of assets to stem its cash drain, such a merger represents a chance to become a major worldwide airline in one fell swoop. For Northwest, a merger would enable it to stave off hostile bidders that might well dismantle it.

But Pan Am must overcome a host of obstacles before closing a deal, not the least of which is shouldering an additional $3.5 billion in debt; it already has about $1 billion. In addition, Northwest has yet to fully digest its 1986 acquisition of Republic Airlines, and its unions are reluctant to endure yet another merger. Finally, the merger must win Justice Department approval at a time when the Government is taking a tougher stance on such deals because of its concern about decreased competition in the airline industry.

But many analysts believe that Pan Am has little to lose. ''They already have so much debt. It's just a matter of degree,'' said Thomas Longman of Bear, Stearns & Company.

Raymond Neidl, an analyst at McCarthy, Crisanti & Maffei, an investment research firm, said, ''It would be a dream deal for Pan Am. It's one of the last chances it has to survive long term.'' Mr. Plaskett announced that Pan Am would join the bidding for Northwest at a shareholders meeting in Washington on May 9. Since then, he has reportedly been working around the clock to arrange financing. Pan Am has commitments of at least $400 million in equity from Prudential-Bache Securities Inc. and the Airlie Group L.P., an investment firm partly owned by the Equitable Life Assurance Society of the United States. An additional $2.7 billion in financing, he said, will come from banks.

PAN AM's bid is one of about four for the airline, which was put up for sale this year after Marvin Davis, the Texas oilman, made a hostile bid. Another suitor is Alfred Checchi, a Los Angeles investor, who owns 4.9 percent of NWA's stock. After rejecting all the bids it received, NWA's directors set a deadline of this Friday for revised proposals.

''As an airline operating company, we bring more to the table than a financial buyer does,'' Mr. Plaskett insisted. Pan Am would not disclose details of its revised bid, but it is believed to be at least $107 a share and could be as high as $120, or about $3.6 billion. Northwest has declined to identify any of the bidders. Mr. Davis's earlier bid was $90 a share, or $2.7 billion.

Northwest has a strong presence in the Pacific. The airline, which used to be named Northwest Orient, controls 24 percent of the traffic from the United States to East Asia and 54 percent of the traffic to Tokyo, its second most profitable destination. Air travel to the Pacific Rim nations is expected to rise 10 percent annually through the year 2000 - double the rate for domestic travel. Pan Am sold its extensive Pacific route system to United Airlines in 1985.

Northwest also co-owns, with Trans World Airlines Inc., the computerized PARS reservation system. Owning such systems is becoming crucial to an airline's success since it extends its marketing reach.

But it is Northwest's vast domestic route system that Pan Am desperately needs. Heavily dependent on the seasonal vacation travel to Europe, the airline's revenues seesaw with the fluctuating dollar. And Pan Am, which is still viewed overseas as the American flag carrier, is uniquely vulnerable to terrorist attacks. Its transatlantic business, for instance, dropped markedly after the bombing of Flight 103 over Lockerbie, Scotland, last December.

Meanwhile, airlines like United and American have expanded their international service. The introduction of smaller long-range airplanes like the Boeing 767 enable airlines to economically operate international flights directly from smaller cities in the United States, thus bypassing the large ''gateway'' cities that Pan Am depends on.

At the same time, European carriers have been expanding their service to the United States, further eroding Pan Am's market share. British Airways, for instance, flies to 22 cities in North America, more than half the number served by Pan Am.